1. Field of the Invention
The present invention relates to the field of communication networks, and more particularly to a cost modeling technique for communication network architectures.
2. Description of Related Art
Many access architectures/topologies are possible for providing subscribers broadband service, including all fiber networks, hybrid fiber/copper networks, DSL (Digital Subscriber Line) broadband networks, wireless networks, and fixed wireless access networks (e.g., hybrid fiber/wireless networks). Numerous factors impact the relative cost of implementing such architectures to varying degrees, including: (1) the type of services offered (e.g., voice, data and/or video) and the bit rates associated with such service types; (2) the network architecture deployed (e.g., wire line, fiber, wireless or hybrid architectures); (3) the service area characteristics, such as service area size, subscriber densities, and service penetration rates; (4) infrastructure and labor costs; and (5) access charges.
Despite substantial bandwidth capacity, all fiber access is generally not a cost-effective option, and, thus, only a small fraction of commercial buildings are served by all fiber access networks. Broadband service may instead be provided by upgrading existing copper facilities using DSL technology. Range limitations of DSL technology, however, require that service providers deploy substantially more DLCs (digital loop carriers) over long loops, or install higher-gauge cables in their networks. Moreover, because of loaded cables and ill-conditioned pairs which are-often encountered in older cables, and which can become noisy at the operational frequency of the DSL, even when within range, not all customers can be adequately served by DSL technology.
Consequently, fixed wireless access networks have emerged as an alternative to all fiber and DSL designs. Worldwide, spectrums for broadband wireless access are being allocated at frequencies from 10 GHz to 42 GHz. Compared to point-to-point implementations, point-to-multipoint millimeter-wave technology, such as LMDS (Local Multipoint Distribution Service), allows one base station to communicate with many customers, thereby reducing the number of base stations required in the network, and, thus, reducing costs. Some of the benefits offered by fixed wireless access include speed of deployment, faster realization of revenue as a result of faster deployment, and lower network maintenance, management, and operating expenses.
Certain factors, however, limit the applicability of fixed wireless access networks. Specifically, rainfall causes signal depolarization of the microwave frequencies allocated for broadband wireless networks, thereby decreasing signal levels and interference isolation between adjacent cell sectors. Also, at millimeter-wave frequencies, communication is line-of-sight (LOS) dependent. Thus, topography and obstructions may prevent some customers within a cell from receiving adequate signal levels. Microwave frequencies are also heavily attenuated by foliage, a fact that has practically eliminated LMDS and other millimeter-wave access technologies for broadband delivery in suburban residential environments. Despite these factors, certain market segments, such as business complexes, may be suitable for fixed wireless access.
Given the various architectures/topologies which are possible for broadband service deliver, and the wide variety of network design options, the need exists for a cost modeling tool which enables a user to recognize the impact of input variables on network node, link, and end-to-end costs.
The present invention is a technique for modeling costs of communication network architectures. Cost models are derived for the network nodes, links, and end-to-end as a function of RF (radio frequency), demographic, traffic, system, and marketing input variables, thereby enabling a comprehensive characterization of network cost in terms of these factors.
In one embodiment, the present invention is an interactive cost-sensitivity analysis tool which allows a user, such as a network designer, to vary network parameters and track the impact of such variables on network node, link, and end-to-end cost. Such cost-sensitivity analysis enables the user to recognize the variation of cost as a function of different input variables, thus facilitating network design and optimization.
In one implementation, the present invention models costs for a fixed wireless access network, providing a cost estimate for provisioning a given service bandwidth to buildings of a service area which is divided into a number of contiguous cells, each served by at least one base station. Demographic parameters, such as serving area size and building density; marketing parameters, such as service penetration rates, i.e., the percentage of potential customers expected to be served; traffic parameters, such as service bandwidth delivered per building; system parameters, such as rain availability requirements, modulation scheme, antenna gain, and hub capacity; and component costs are considered. The size of each cell is determined by taking the minimum of three constraining radii to ensure that both capacity and coverage requirements of the network are satisfied. More specifically, the minimum of: (1) radio rangexe2x80x94a function of the modulation scheme implemented by the base station transmitter; (2) rain radiusxe2x80x94a function of the geographic rain zone, rain availability requirements, signal polarization, and receiving antenna gain; and (3) hub capacity radiusxe2x80x94a function of allocated bandwidth per cell, spectral efficiency, service bandwidth requirements, building density, and penetration rates, is determined.
The cost model estimates lengths/cost of the feeder network, i.e., the backhaul network connecting each hub to a service node, as a function of the previously determined cell size. Thus, the impact on the feeder network and end-to-end network cost of input variables, such as modulation scheme, antenna-type, bandwidth demand, penetration rates, rain availability requirements, and rain zone, can be recognized by considering total cost as a function of cell size, thereby facilitating cost-efficient network design.